The present invention generally relates to apparatus and methods for forming tires and, more particularly, to apparatus and methods for forming tires on a drum.
Tires may be fabricated by placing several tire components on a first drum so as to form a cylindrically-shaped tire carcass in a first stage of the tire-forming operation. The tire carcass may then be run through a second stage of the tire-forming operation by being transferred from the first drum onto a second drum where the tire carcass may be expanded into a toroidal shape and where additional components are applied, such as a belt package and rubber tread. The expanded carcass is then molded and vulcanized into a finished tire. Unfortunately, this fabrication process is time-consuming and requires two different drums, which adds complexity to the tire-forming operation.
To address this complexity, single-stage drums and related methods have been developed. In a known type of operation involving single-stage drums, a plurality of layers of material are applied onto a drum that has shoulder and center sections that are axially and radially movable. Movement of these sections permits forming of the layers of the tire carcass and expansion of the tire carcass on the same drum.
There are drawbacks with this type of operation, however. For example, apparatus with single-stage drums require stitching of apex bead components of the tire carcass over other layers prior to radial expansion of the carcass, which adds complexity and the time required to complete the operation. Additionally, complex controls are required to coordinate the axial and radial movement of the shoulder and center sections so as to prevent trapping of air in the tire carcass. Yet further, that type of operation involves stretching and relaxing of the rubber layers, which may result in permanent deformation of the rubber. This deformation in some cases leads to unpredictable placement of the rubber layer endings, which may be detrimental to tire uniformity.
Accordingly, a need exists for tire-forming apparatus and methods that address these and other drawbacks associated with conventional tire-forming apparatus and methods.